1. Week 1 - Friday
CS 113

2. Last time What did we talk about last time?
Syllabus and course policies
A little bit about computers

3. Questions?

4. Graphics

5. Screens
Ultimately, most graphics that we're interested in on a computer are displayed on a screen
A screen is made up of dots
Each dot is called a pixel, short for picture element
Each pixel has a color
By displaying enough pixels, you can make a picture

6. Resolution A screen has both a width and a height in pixels
The combination of these is called the resolution of the screen
Higher numbers mean more pixels, allowing a more accurate representation of images
Device
Resolution
iPhone 4
960 x 640
iPhone 6
1334 × 750 
Older monitor
1024 x 768
720 HD TV
1280 x 720
1080 HD TV
1920 x 1080
4K monitor
3840 x 2160

7. Aspect ratio
It's difficult to create programs and video content that looks good on any arbitrary screen size
Many screens have one of three different aspect ratios (the ratio between width and height)
Why are there three different ones?
Aspect Ratio
Example
Devices
4 : 3
1024 x 768
Standard definition TVs, older monitors
16 : 9
1920 x 1080
High definition TVs, many newer monitors
16 : 10
1280 x 800
Some newer monitors

8. Buying a TV Many of you will buy a TV (or a monitor) at some point
HD TVs will all have a 16 : 9 aspect ratio
A 1080 TV has more than twice as many pixels as a 720 TV
Contrast ratio is the ratio between the brightest (maximum white) and the darkest the screen can show
A higher contrast ratio makes a more vibrant image
There are 1080p and 1080i TVs (similar for 720)
p is for progressive and i is for interlaced
Interlaced is an old standard based on how TV signals used to be sent
Progressive is clearer and easier to look at, especially for text

9. Working with graphics
In order to program graphics in a computer, we'll have to think about the screen (or some part of it) as a Cartesian coordinate system
In some systems, y starts at 0 at the top of the screen and increases downward
In other systems, y starts at 0 at the bottom of the screen and increases upward x y
(0,0) x y
(0,0)

10. Scratch
For the first few weeks of the semester, we'll be using Scratch to program with
Scratch puts x and y in the middle, with positive and negative values, like a normal Cartesian plane x y
(0,0)

11. Scratch Tutorial

12. Lab 1

13. Upcoming

14. Next time… Back to computers More on graphics
We will start 3D graphics

15. Reminders
Pick your teams for Project 1 if you haven't already!